Monitoring Durability of Limestone Cement Paste Stored at Conditions Promoting Thaumasite Formation

The durability of Portland-limestone cement with high limestone content was monitored at conditions promoting thaumasite formation. Pore structure and deterioration characteristics were assessed with X-ray micro-computed tomography and correlated with material‘s strength. Changes in crystalline and amorphous phases of the cement paste were investigated with X-ray powder diffraction and solid state nuclear magnetic resonance spectroscopy. Rapid deterioration was observed, evolving as a front causing concentric crack patterns followed by detachment of the part of specimen in contact with the corrosive solution. This ultimately led to loss of structural integrity after 4 months of exposure. During sulfate attack, thaumasite, ettringite and gypsum formed at the expense of portlandite, calcite and monocarboaluminate hydrate. Furthermore, polymerization of silicate chains in C-S-H and deterioration of C-S-H also occurre

Water‐resistant latex coatings: Tuning of properties by polymerizable surfactant, covalent crosslinking and nanostructured ZnO additive

This paper deals with the development of acrylic latexes providing high‐performance wa-ter‐resistant coatings. For this purpose, mutual effects of anionic surfactant type (ordinary and polymerizable), covalent intra‐ and/or interparticle crosslinking (introduced by allyl methacrylate copolymerization and keto‐hydrazide reaction, respectively) and ionic crosslinking (provided by nanostructured ZnO additive) were investigated. The latexes were prepared by the standard emulsion polymerization of methyl methacrylate, butyl acrylate and methacrylic acid as the main mon-omers. The addition of surface‐untreated powdered nanostructured ZnO was performed during latex synthesis, resulting in stable latexes comprising dispersed nanosized additive in the content of ca 0.9-1.0 wt.% (based on solids). The coating performance with emphasis on water resistance was evaluated. It was determined that the application of the polymerizable surfactant improved coating adhesion and water‐resistance, but it wasn′t able to ensure high water‐resistance of coatings. Highly water‐resistant coatings were obtained provided that covalent intra‐ and interparticle cross-linking together with ionic crosslinking were employed in the coating composition, forming densely crosslinked latex films. Moreover, coatings comprising nanostructured ZnO additive displayed a significant antibacterial activity and improved solvent resistance. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Youth and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [LM2018103]; Czech Academy of Sciences, Institute of Theoretical and Applied Mechanics [RVO 68378297]; TBU in Zlin [IGA/CPS/2020/001]RVO 68378297; IGA/CPS/2020/001; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: LM2018103; Akademie Věd České Republiky, AV Č

Comparison of Terbutryn Acute Toxicity to Danio rerio and Poecilia reticulata

Abstract The aim of the present study was to determine and compare acute toxicity of terbutryn in Danio rerio and Poecilia reticulata, and in two different developmental stages of D. rerio -embryonic and juvenile. Acute toxicity tests were performed according to OECD methodology. The LC50 values were assessed by probit analysis using EKO-TOX 5.2 programme. The 96hLC50 terbutryn mean value of 5 tests was 2.85 ± 0

Intangible assets and tangible assets in accounting in Czech Republic (accounting and tax view)

Intangible property and tangible investment goods constitute to be one of the most essential problems not only in the science of accounting but also in the sphere in taxation. That is the reason why this graduation thesis aims to offer a summary of the complete investment goods turnover starting from its acquisition and evaluation, continuing through its depreciation and finishing with its retirement. As its further aim this thesis tries to explain the difference between the investment goods and the low-value tangible assets. The last chapter is dedicated to the deferred tax which comes as a result of different tax and accounting depreciations. Examples from the practice give an additional depiction of the problem

Comparison of the spectra of Vaseline samples using Fourier transform infrared spectroscopy

The aim of the report was the comparison of 6 spectra of Vaseline samples. The spectra were collected using Fourier transform infrared spectroscopy (FTIR) in the attenuated total reflection (ATR) mode

Profit and loss in the insurance sector in the Czech Republic

The graduation thesis aims to specify and define, with respect to the Czech legislation, the profit and loss statement of the insurance companies and those items of revenues and expenses that are specific for the insurance companies. The thesis deals with the principal characteristics of the revenues and the expenses of the insurance companies as well as with the matter whether insurance companies can in any means influence their management result. It also focuses on the field of the insurance security -- what is the insurance security in the Czech Republic in relation to the European Union, and on the quantity limits of the profit and loss statement, in the Czech insurance sector. It also assesses the efficiency of the local insurance companies in relation to this, what is the share of the earned premium when taking in account the insurance claims, the operating costs and the management result. The graduation thesis came to the conclusion that an insurance company can quite easily influence its accounting management result and therefore it is necessary for the company to respect the relevant accounting measures. Furthermore, the Czech Republic in comparison to the other EU countries indicates relatively low level of insurance security. With respect to the efficiency it is possible to conclude (in relation to the year 2012 and the local insurance companies) that the earned premium comprises of more that 60% of the claimed damages, 30% of the operating costs and 10% of the earned premium represents the net profit

Mechanisms of controlled crystallization of struvite-K by NTA and EDTA sodium salts

The mechanisms by which ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) sodium salts control the precipitation of struvite-K from solution have been investigated at room temperature, pH = 9, two degrees of supersaturation and two stirring speeds. The interest spans from the potassium and phosphorus recovery from wastewater, the prevention of scale deposits in wastewater treatment plants, to the modification of magnesium phosphate cement reaction. Both molecules influenced the spontaneous precipitation by extending the induction time, reducing the apparent rate of crystallization and the amount of reaction product. When adding 20 mM of EDTA, at the highest supersaturation degree, the rates dropped from 2.14 min-1 and 4.09 min-1 to 1.36 min-1 and 1.71 min-1, under fast and slow stirring speed conditions, respectively. Conversely, at lower supersaturation the precipitation was almost completely inhibited. Similar inhibiting effect was observed for NTA. The additives were found to influence the reaction path by exploiting their complexing ability in solution, thus depressing the supersaturation degree in Mg2+ ions with respect to struvite-K, and by molecular adsorption at the forming solid surfaces, hindering nucleation and crystal growth. The surface adsorption process has been confirmed by the more negative zeta potential measured on the crystals (from −14.5±1.0 mV to −17.0±1.6 mV and −20.8±3.0 mV for EDTA and NTA, respectively). Both additives induced an overall reduction in crystal size (up to 85 %) and a reduced elongation of the precipitated crystals (aspect ratio decreasing from 2.3 to 1.3 and 1.7 for EDTA and NTA, respectively) in consequence of the preferential adsorption at the (101) and (¯101) faces